Telegraph system



Oct. 5, 1937. E. E. KLEINSCHMIDT TELEGRAPH SYSTEM Filed Sept. '20, 1930 2 sheets-she t 1 INVENTOR Edward [{Yahmbzm'd? BY MW ATTORNEY Oct. 5, 1937.

E. E. KLEINSCHMIDT "TELEGRAPH SYSTEM Filed Sept; 20, 1930 2 Sheets-Sheet 2 INVENTOR Eda 4rd zfzm/wmmw 9 ATTORNE .5

Patented Oct. 5, 1937 UNITED STATS PATENT OFFICE TELEGRAPH SYSTEM Application September 20, 1930, Serial No. 483,348

21 Claims. v (01. 1784.1)

The present invention relates to telegraph systems. More particularly the invention relates to telegraph relaying and switching systems embodying automatic apparatus for effecting communication between a central station and a plurality of outlying telegraph stations. In telegraph systems, the present day practice is to receive all the incoming messages for a large city at a central or main distributing station. This central station is connected to a plurality of scattered sub-stations located in various parts of the'city by radial telegraph lines. The messages received at the central station are re-transmitted therefrom over one of these lines to the particular sub-station located nearest the final destination of the message and from which the message is transmitted by messenger to its destination. Similarly messages for transmision must be delivered to an outlying sub-station then transmitted to the central station, and then retransmitted to the remote destination.

In order to handle the signalling traffic in such prior systems, a large number of telegraph sets were located at the central stations to receive messages from or send messages to each of these outlying stations, and message delivery service was maintained at sub-stations where messages for outside delivery were received. To handle the message traffic eiiectively it has been the practice to utilize at central stations, an independent telegraph set for each outlying station which is expensive, or, by complicated switching apparatus the number of sets of apparatus has been reduced.

Inasmuch as the signalling traffic handled at central stations during peak periods is heavy it is desirable to facilitate quick connections from the central station instruments to any sub-station and provide simple and reliable supervision of the sub-station line by the central station operator so as to avoid unnecessary attempts to seize busy lines. Since the signalling trafiic varies from a peak load to a comparatively low load, in accordance with the present invention, novel flexible control of the destination of incoming calls at the central station is provided whereby the total trafiic may be concentrated upon a minimum number of operators during hours of low traflic, and is distributed or separated into different' classes of traffic during hours of heavy traffic.

, Accordingly an object of my invention is to provide novel systems and apparatus for handling incoming and outgoing traffic in telegraph cen variably as the message trafiic varies to secure maximum efliciency and economy of operation.

Still another object of my invention is to provide novel methods and apparatus for routing telegraph trafiic at central or relay telegraph stations.

Still a further object of my invention is to and for checking the identity of any busy line.

In a signalling to a remote printer station, the operator at the remote station may not at the particular moment be at the instrument. For effective service the calling operator, however, must know whether a remote printer is in con.- dition to receive the message Heretofore it has been necessary to await signalling from the remote operators for such information which results in a great deal of delay in the existing systems. r 7

Accordingly a further object of the present invention is to provide novel means for automatically indicating the condition of sub-station apparatus at the central or relay station.

Further objects of my invention are to provide novel meansfor maintaining the sub-station motors normally non-operative when no messages are being transmitted therefrom and starting them into operation when the central or relay office is in condition to receive a message; to provide novel audible busy signals in addition to the visible signals at a central office; to provide novel signalling means at sub-stations to indicate that a message is being received; to provide revertive test means by which a central or relay oflice attendant may determine positively that the sub-station motors are running, and that the selecting elements of the sub-station are working; and to provide novel means for performing all of the above described operations over a single line wire. 7 i

Still further objects of the present invention are to provide automatic switching and message distribution systems in which a minimum amount of apparatus is employed to serve any given number of signalling lines, which facilitates quick automatic connection from a sub-station to central or relay station apparatus, provides for simple and reliable supervision of sub-station'lines by attendants, provides flexibility in the control of the destination of calls coming to the central or relay station for concentrating the total traffic upon a small number of operators during hours of low traflic and properly distributing the trafiic during hours of heavy traific; in which complete control of all outlying station telegraph sets is obtained by the central station operator when once a connection is made to an outlying substation; in which a busy identification of all the lines in operation is provided at all times; and in which the condition of a remote apparatus is at all times under supervision of an attendant.

Further objects of this invention will appear in the following description of the preferred embodiment of the invention and are such as may be secured by the utilization of the combinations, sub-combinations and principles hereinafter set forth and as defined by the terms of the appended claims.

Referring to the drawings.

Figure 1 shows in diagram a relay station embodying the present invention.

Figure 2 shows in diagram the equipment at outlying stations embodying the present invention.

In the specific embodiment of the invention as shown in the drawings, the central or relay office of Figure 1 is provided with printing telegraph sets and 2 in sufiicient numbers to handle the total trafiic, and also with automatic switches 4, one for each sub-station line, each to handle the incoming traflic of its line, and with automatic switches 5 suflicient to handle the outgoing traffic of the central station.

The telegraph sets I and 2 are identical and each such set comprises power plug II, ballast resistance I2, sender I3, printer I4, polar relay I 5 and switching plug I6, all connected in a series circuit from a source of power to the tip of the plug I6. Points of relay I5 (shown charged and operated in telegraph set I) control an obvious circuit through the winding of slow-to-release relay II. Points of relay II (shown operated) control an obvious circuit through winding of quick-break relay I8 (shown charged) which closes an obvious circuit for motor I9 to furnish mechanical power required by sender I3 and printer I4. Relay I5 has mechanical biasing spring 20 to open its points when its winding is not charged by current.

Each set has also release key 26 and testing key 21, the latter shunted by resistance 28, and both keys included in a circuit from earth through power plug II, wire 29, points of relay II, key 26 and key 2! to body member of switching plug I8.

The printer and/or receiving perforator operated by a selector magnet I4 and the transmitter I3 may be of any type, such as described in the patents to Krum 1,595,472 issued August 10, 1926, and to Kleinschmidt 1,567,392 issued December 29, 1925.

Work tables 3| and 32 are provided identical in apparatus but differing in circuit connections, because the tables are connected electrically in pairs, and external telegraph circuits pass through one table and terminate at the other.

The equipment of each table, 3| and 32, comprises a power jack 39, two switching jacks, 31

for sending and 38 for receiving, a signaling dial.

39, a manual ringing key 49 and a busy signal 4|. The dial 39 has the resistance 42.

Power jack 36 comprises the contact member 46 connected to earth, and the contact member 41 connected to a source 48 of direct current, earthed. Dial 39 is of well-known telephone type and comprises a pair of contacts 5| normally closed, which may be operated manually in code manner to give any desired number of consecutive brief breaks, and also a pair of contacts 52 normally open, which are closed at any time that contacts 5| are open.

The telegraphic circuit connections of the pair of work tables 3| and 32 are as follows: a sending telegraphic line wire 55 and its extension 56 are connected in circuit from earth, winding of signal relay 57, wire 59, points of cut-through relay 59, wire 55, points 5| of dial 39 on table 3| normally closed points of manual switch 40, closed points of jack 35 without plug, wire 56, points 5| on table 32, key 49, points of jack 3! condenser 60 to earth. There is no current. This circuit includes busy signal 4| on table 3| shunted by points of jack 31 and also busy signal 4| on table 32 shunted by points of jack 3I.

Holding wire and its extension 56, associated with wires 55 and 55, are connected in circuit from an open point of off-normal switch 61,

points of slow-release relay I58, points of relay 59,

wire 55, to body member of jack 31 on table 3| through points of jack 3! without plug, wire 66, to body member of jack 3! on table 32.

A receiving telegraphic line wire I0 and its extension II are connected from an open point on the switch 4, wire I9, points of jack 38 without plug on table 32, wire I! to tip spring of jack 38 in table 3|.

Holding wire 12 and its extension I3, associate-d with wires I9 and II, are connected in circuit from an open point on the switch 4, wire I2, points of jack 38 without plug on table 32, wire 53, points of jack 3% on table 3|, to earth.

A table such as Si is associated with each switch such as 5, and a table such as 32 is associated with each circuit wire such as 79. Each table may have extension wires to another table.

To assemble the apparatus for service, portable set I is brought to the fixed and wired table 3|. Power plug II Switching plug I6 then may be inserted in jack 3! whereby set I may co-operate with switch 5 as a sending set; or in jack 38 whereby set I may cooperate with switch 4 as a receiving set. In the figure, set I is connected for sending and set 2 for receiving.

When a set as 2 is connected for receiving messages, no action results until a message is about to be received. When a set as I is connected for sending, the motor-starting mechanism operates.

When plug I6 is inserted in jack 3?, table 3|, a circuit for current is established from source 38, jack member 41, plug II, ballast I2, sender I3, printer I4, relay I5, tip of plug I6, tip spring of jack 3?, switch 49, points 5|, wire 55, points of relay 5%, wire 58, winding of relay 5! to earth. Relay 5! is operated and operates relay 98 over an obvious circuit. Relay I5 is operated (as shown) and operates relay I1 (as shown) which operates relay I8 (as shown) to operate the motor I9. Set I now is in control of switch 5 for outgoing messages.

Switch 5 is of well known type as used in telephone systems. It comprises two sets or banks of fixed contact plates, upper bank I6 and lower bank II. Two movable contacts or wipers I8 and I9 cooperate with the banks I6 and I1 respectively, and each wiper may engage any contact in its bank by being moved in stepping manner, first vertically by mechanical action of vertical magnet 80 and then horizontally by mechanical action of horizontal magnet 8|. The wipers I8 and I9 when advanced are held by dogs not shown which may be withdrawn by release magnet 82,

is inserted in power jack 35.

when a spring not shown will move'the wipers to the left and gravity will move them downward to normal position shown. This'switch is well known and is described in further detailin Chapter 3, Automatic Telephone Practice, published by H. E. Hershey, 1001 W. Van Buren St., Chicago (1920)."

Set I controls switch 5 through dial 39 and a set of relays shown in the rectangle93. Slow release relay '68, series relay 84 and busy relay 05 are of the slow-to-release type. The off-normal switchv 61 is in the position drawn when the wip ers I8 and I9 are normal as shown. At other times, switch 6.! has its .contacts reversed. In operation, to cause wiper l8 and "I9 to engagecontacts88 and 89, the operator at set I manipulates dial 39 to break points 5| three times, meanwhile closing points 52 to preserve current through printer I4 through the circuit,

source 48, jack member 41, plug II, ballast I2, sender I3, printer I4, relay I5, tip of plug I6, spring'of 'jack 31, switch 40, points 52, resistance 42 to earth. Three successive breaks of points 5| releases the armature of relay 51 three times.

Firstrelease of relay 51 connects earth through points of relay 51, points of relay 68, points shown closed in switch 61, winding of relay 84, winding of vertical magnet 80 to battery, operating magnet80 once, operating relay 84, lifting wipers I8 and 19 one step and shifting the points of switch 61. Second and third releases of relay 51 con nects earth through points of relay 5'I, points of relay 68, lowest points of switch 67, points and winding of relay 84, winding of magnet 80 and to, battery. Magnet 80 operates twice and wipers I8 and I9 make two more steps upward, thus stopping at the levels ofthe contacts 88 and 89. Relay 84 releases.

The operator at set I now manipulates dial 39 to break points 5Itwice, releasing relay 51 twice, and twice closing circuit from earth through points of relay 51, points of relay 68, lowest points of switch 61, points of unoperated relay 94, lowest points of relay 59 and magnet BI to battery. Magnet BI operates twice and steps the wipers I8 and I9 two steps to the right, to engage the contacts 88 and 99. As shown, the lower. winding of relay 85 is in shunt with the winding of magnet 8| and relay 85 has been operated and now connects source 96 of alternating current through lower points of relay 85, wire 55, points 5I, switch 40, signal device 4I (its shunt points in jack 3? now are open) wire 56, points 5I of table 32, switch 40, points of jack S'I, condenser 69, to earth.

Should the selected line be busy, an earth con nection will be found upon contact 88 as described later. This will energize the upper winding of busy relay 95 over a circuit from battery through upper winding of relay 85, points of relay 85 (operated) wire 9!, wiper I9, contact 89 and earth. The continued circuitfrom source 99 to signal device 4| will operate the device 4| to notifythe operator at set Ithat a busy line has been engaged.

Should the line be not previously busy, relay 95 will release its armatures and (assuming that switch'4 pertains to the line selected) then engagement of I9 and 89 will form a circuit from battery through winding of magnet IOI, contact points of magnet I I wire I02, wire I 93, winding of cut-off relay I94, wire I95, wire I96, wire I01, contact 89, wiper l9, wire 9|, points of released relay'85, upper winding of relay 59 to earth. The current is not enough to operate magnet IIlI nor relay I04 but moves the armature of relay 59 enough to close the circuit of the lower winding of relay 59 whereupon relay 59 operates its contacts fully and is held operated through key 26 by the circuit from battery, lower winding of relay 59, points of relay 59, wire 65, body member of jack 31 on table 3|, body member of plug I6, key 21, key 26, points of relay I'I, wire 29, plug II, jack member 46 to earth. This circuit may be opened only by the operator at set I, by operating key 26 or by removing plug I6.

The full operation of the points of relay 59 connects the wire 65 to the wiper I9 and thus earth from jack 36, through key 26 and wire 65 is connected to wiper I9, contact 89 and through wires I0'I'and I06 to other contacts as 89 in other switches as 5, thus providing the earth for busy test as mentioned above under the conditions should the selected line be busy.

The points of relay 59 also open the circuit of rotary magnet 8| to prevent it from moving the wipers I8 and I9 further.

The points of relay 59 also open the circuit of relay 57 and connect the signal wire 55 to the wiper l8 and contact 98 and thence to wire I08, wire I 99 and further as will be described in the general description of operation of the system.

Inward service is effected through switch 4 acting under initial control of sub-station I20.

Sub-station I20 comprises sender I2I, printer I22, points I29, polar relay I25, motor relay I26 and calling key I21, which may be such as the dial 39, all connected from earth to line I 30 in series. Points I23 are shunted by points I3I. Relay I25 has points to shunt the winding of relay I26 and key I27, or alternatively tov shunt the sender I2I. Relay I26 when deenergized closes circuit through the winding of relay I33 which in turn closes an obvious circuit to operate the motor I34. A signal device I35 in series with condenser I36 is connected from line I30 toearth. Operation of sub-station I20 will be described in connection with operation of switch 4.

Switch 4 has three levels of contacts I4I, I42, I43 shown with fifteen contacts in each level, and three double-end wipers I44, I45, I46 engaging respectively one contact in each level at all times. Ratchet I41 steps all wipers and is stepped by pawl I48 on stepping magnet IOI.

See chapter 11 of the Hershey book cited.

Supervisory relay I49 is normally charged. Line relay I59 starts the stepping action of switch 4. Batteries II and I52 are reversed in polarity as compared with all other batteries in the figures.

In operation, wipers I44, I45, I46 are normally on their first contacts as shown and relay I49 is normally charged by current from reverse battery I55, winding and points of relay I49, points of relay I04, wire I52, line wire I30, sub-station I to earth. This current operates polar relay I to open its points and charges relay I26.

To call, operator at sub-station I20 opens calling key I21 briefly. Opening key I21 breaks current throughl relay I49 and releases relay I49, then upon closing key I2! the circuit is through relay I59 instead of relay I49, thus operating re lay I50. Stepping magnet I9I operates by current from battery through winding and then points'of magnet I [II points of relays I50 and I94, wiper I45 to earth, and it operates repeatedly as long'as earth (busy condition) is found on successive contacts of level I42. Earth at wiper I45 has shunted the winding of relay I04, and when that earth is absent the relay I64 will be operated by current from battery through winding and points of magnet IOI, wires I02, I03, relay I04, wire I54, points of relay I50 to earth. Relay I04 operates its armatures I51, I58, I59 to close their front points.

Armature I 51 recharges relay I49 over an obvious circuit. Armature I58 connects earth from points of relay I50 to wiper I45.

Armature I59 closes a telegraph line circuit from battery at receiving table 32, through power plug II, ballast I2, sender I3, printer I4, relay I5, tip of switching plug I6, receiving jack 38, wire 10, wiper I44, front point and armature I59, wire I53, line wire I30 and sub-station I20 to earth. The current is full telegraphic operating volume and of such polarity that relays I5 and I25 close their points, operating relay I1 and releasing relay I26, thus operating relay H8 and I33 and starting motors I9 and I34. Thus telegraphic communication is established between sub-station I20 and receiving table 32.

Armature I59 stops current in relay I50 but the slow armature of relay I50 does not remove earth from wire I54 until afteranother earth connection has been supplied to wire I54, from earth at table 32 through power plug II, wire 29, points of relay I1, key 26, 21, body of plug I6, body member of jack 38, wire 12, wiper I45, armature I58 and front point to wire I54. Thus the relay I04 passes to sole control of key 26 of table 32. The inward message now may be transmitted.

For restoration to normal, key 25 is opened briefly, releasing relay I04, whereupon armature I59 disconnects line I30 from table 32 and conneets line I30 to relay I49, restoring the normal supervisory current which has such polarity that polar relay I25 opens its points, removing shunt from relay I26 which operates its points to open relay I33 which opens its points to stop motor I34. Armature I59 stops current in relay I5 which opens its points, releasing relay I1 and I8, thus stopping motor I9.

Armature I 51 closes a restoring circuit for stepping magnet I| through wire I02, back points of relay I58, wire I6I, wiper I46, contacts I43, wire I62, armature I51 to earth. Magnet I0| operates repeatedly until all wipers reach normal as shown which opens the restoring circuit, thus completing the operation for an. inward message.

For transmission of an outward message, operator at table 3| dials as described above, connecting wipers 18 and 19 to contacts 88 and 89. Two circuits result, a telegraphic service circuit through wiper 18 and a private circuit through wiper 19.

The private circuit extends from battery, winding and points of magnet I0| (not operating) wire I02, wire I03, relay I04 wires I05, I06, I01, contact 89, wiper 19, points of relay 59, Wire 65, jack 61,.plug I5, keys 21, 26, points of relay I1, wire 29, power plug II and to earth at table 3|. Relay I04 operates armature I51 to close its front point and operates armatures I 58 and I59 to open their back points but not to-close their front points. Armature I59 removes relay I49 from line I30 and armature I51 holds relay I49 charged.

The telegraphic service circuit extends from battery at table 3|, through plug II, ballast I2, sender I3, printer I4, relay I5, tip of plug I6, spring of jack 31, switch 40, points wire 55, points of relay 59, wiper 18, contact 88, wire I06, wire I09, wire I30 and sub-station I20 to earth, operating relays I25, I26 and I33 to start motor I34. Outward messages now may be transmitted.

For restoration to normal, key 26 of table 3| is operated briefly; Key 26 releases relay I04 which permits armature I59 to connect line I30 to relay I49, reversing polarity upon wire I30 and operating relays I25, I26, and I33 to stop motor I34. Key 26 also releases relay 59 which charges magnet 82 by current from battery, magnet 82, top points of switch 61, back points of relay 68, back points of relay 59, wire 65, jack 31, plug I6, key 21, key 26, points of relay I1, wire 29, plug II to earth. Magnet 82 restores switch 5 as has been described.

The general operation of the system as thus far described is as follows: To transmit an inward message, the sub-station or calling operator operates a starting key. The automatic line switch at the relay ofiice allotted to his line is immediately started into operation to select an idle telegraph set. When such a set has been found, a connection is made between the calling and called set. The sub-station motor will start and the operator may then proceed to send the message at once. The simple act of operating a key connects together a sub-station telegraph set and a central station telegraph set which may be a receiving printer and/or a perforator adapted to record the message in form for re-transmission.

This connection may be terminated only by a key at the central station telegraph set, so that the central or relay station attendant may send to the sub-station any inquiry, request or formal acknowledgment of the message before disconnecting the line. In other words, in the specific embodiment disclosed, the central or relay station has at all times, full control of the signalling line, irrespective of whether the connection originated at the central or relay station or at the remote sub-station. This result is accomplished in the specific embodiment disclosed by maintaining the release magnet of the automatic switch independent of sub-station control at all times.

To send a message from the central oilice to a any sub-station to which messages are to be sent, the central station office attendant dials the number of the line on a dial of the telephone type to establish the proper connection. The message may be then transmitted without waiting for any manual response from'the sub-station.

Dialing the number operates an automatic switch to select the desired line to the outlying station. When connection is made to the substation line, automatic devices at the sub-station operate to start the sub-station motor and to condition the sub-station apparatus to receive the message without cooperation of an attendant.

When the connection has been established, with the central or relay station, telegraphic transmission in either direction may be efiected, and connection may be released only by the central ofiice operator.

While the signalling traffic is heavy, it is desirable that independent telegraph sets employed for the outgoing signals and. for the incoming signals be separately grouped since one receiving operator may attend several machines. When, however, the traific becomes light, it is preferable to operate two adjacent sets for the two classes of signalling. This change in grouping is accomplished by switch plugs I6 and jacks 31 and 38. When a sole operator with a sole sending set is carrying the early morning traffic, all plugs I6 are pulled other than, first, the set in use for sending, and, second, one or more Visual busy signal 'Eachline as I30 has a lamp as I33 in a lamp bank I64 connected from battery to its private Wire as -Iiiii. When the line is engaged by any sending table as 3|, a circuit for the lamp will be formed, from battery, lamp I63, wire I65, Wire I 05, Wire Iil'I, contact 89, wiper I9, points of relay 59, wire 55, jacktl, plug I5, key 21 shunting resistance 23, key 25, points of relay I'I, wire 29, jack II to earth. When 'the line has engaged any receiving table as 32', a circuit for the lamp will be formed, from battery, lamp I63, wire I55, wire I06, Wire I05, wire I5 3, armature I58, wiper I45, Wire 12, jack 3B, plug I6, key 21 shunting resistance 28, key 25, points of relay I'I, wire 29, plug II to earth.

During the time that any telegraph sets at the central station and remote station I20 are connected, lamp IE3 is illuminated over a circuit as traced above to indicate that the line I30 is busy.

Since, however, a number of lamps may be illuminated it may be desirable for the operator to check the line with which he is connected. This is accomplished by opening and closing key 21 to'change the resistance in the circuit of the lamp I53. By observing which lamp flickers by thisoperation, the dispatcher will be apprised of the line with which he is connected. Further a glance at the lamp bank will protect the operator from wasting time by dialing for a busy line.

Answer-back system An answer back system whereby the sub-station automatically responds to a test signal from the central office is provided. In the embodiment disclosed the added equipment comprises only the contact I23 which is open when the printer is in the'shift position, and the contact I3I which is opened briefly by the act of selection which corresponds to the selection of the letter M. The open interval thus attained corresponds in time value to the spacing interval of the start pulse in a", start-stop system. There is no added equipment at the central office.

The operation of the answer-back comprises sending the successive code signals, for example, a shift signal and an M-character signal, in response to which the sub-station automatically transmits an unshift signal. The shift signal has shifted'the central office printer and the unshift signal restores the central office. printer mechanismto normal which indicates to the central operator that the sub-station selecting devices are, operating properly and have received and interpreted properly the. signalfshift and the signal Calling the sub-station At sub-station I20, a signalling device I35 which may take the form of the tuned harmonic ringer of. telephone party-line practice, is connected in series with condenser I36 from earth to;,the signaling conductor I30. On each work table 3l 32, is a manual switch 40 adapted to shift the wire 55 or 56 from jack 3'! to source I65 of alternating current, and a further manual switch I68 adapted to shift the wire III or II from jack 38 to source I 65.

The line I30 is seized and a message is sent Without awaiting response of the sub-station. However, at times, a central oflice attendant may desire to obtain direct communication with an attendant at a sub-station, as for instance, when an immediate answer toan inquiry is wanted. By operation of manual key 40 at the central station, an audible signal at the sub-station may be sounded. The central office operator being connected with the line. through either automatic switch 4 or 5, may sound the signal until the sub-station is operated in response. The signal device I35 of the substation is tuned to respond to the alternating current from source I65 but does not respond to telegraphic service signals.

The central operator further may operate the key either before or after sending a message tosound the signal to call attention to the message.

I Busy-signal system In the level I 420i switch 4, fifteen contacts are shown, the fifteenth being shown insulated. In level I4I, the fifteenth contact, III, is connected to source I'IZ of alternating current.

In the event that all receiving apparatus is busy, the wipers move from contact to contact until they reach their fifteenth contact where they will stop because relay I04 is not shunted and magnet IflI can not operate. Relay I04 operates and connects the calling line I30 to source I12, thus sounding the signal device I35 at substation I 20 by current over the circuit from source I72, contact I'II, wiper I44, armature I59, wire I53, wire I35, condenser I35, signal device I35 to earth. Relay I04 has opened the circuit of the winding of relay I50 which after a brief intervalreleases its armature and opens the circuit of relay I34 which releases its armatures to stop the signal and to close the restoring circuit for switch 4.

The sub-station attendant then may operate calling key IZ'I again, either at once or after a suitable interval.

Dial-switch shunt A dial 39 is provided individual to each work table. The attendant by operating the dial transmits signals to operate the automatic switch 5 and seize a predetermined signaling line extending to an outlying station. Dial 39 is of the usual type employed in automatic telephony and comprises in part a switch 52 which is connected to resistance 42 and to earth for temporarily maintaining a circuit closed through the local telegraph set while the dial opens and closes points 5I for signaling. This avoids any action by the printer I4 which otherwise might result from dialing were the dials to interrupt current through the printer magnets.

General operation with special features The improved system offers the. optimum facility for enabling the central sending operator to do a maximum. amount of work. The system of visual busy signals or lamps enables him to avoid loss of time in useless dialing, and, when a desired line is noted as available and is connected by dialing, the automatic starting of the motor at the sub-station enables the central operator to send the message at once without waiting. The answer-ba/ck signal gives him confidence in his work and assureshim that he is not sending to the birds.

One receiving operator may serve several receiving sets, and, as each received message is inspected, the operator is not required to recall the sending station since the holding circuit controlled by key 26 will have held the connection in readiness for any inquiry. This feature becomes of material value in the case of a message in which the sending operator has neglected to identify his sub-station.

When a central operator finds a sub-station irresponsive, his procedure is as follows: Operate key 26 and observe the busy-signal variation, to assure his connection to the proper line. Send shift signal and M-character signal and observe the answer-back signal to assure the operating condition of the station. Then'operate the audible signal with key 48 or I66 and send messages with sender l3 until the sub-station responds by operating sender I2l. There is provided thus an optimum of simple routine tests and signals to attract the attention of the proper sub-station.

Although I have shown my invention as applied to a preferred embodiment thereof, it will be clear that it may be practiced in many other forms and I do not intend to limit myself to the arrangement shown, but only insofar as set forth in the appended claims.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What I claim and desire to secure by United States Letters Patent is:

1. In a signalling system, a central station, a plurality of sub-stations, normally non-operating telegraph apparatus at each of said sub-stations, a single signalling line extending from the central station individual to each of said substations, switching equipment at said central station, normally non-operating telegraph apparatus for outgoing messages at said central station, plug-and-jack switching means for connecting said outgoing telegraph apparatus to said switching equipment, means responsive to said connection for conditioning said outgoing telegraph apparatus for operation, means for variably operating said switching apparatus to select one of said signalling lines individual to a sub-station, means at said sub-station responsive to the selection of said signalling line for conditioning said telegraph apparatus thereat for operation with said central station apparatus, and means operative following the connection with said substation whereby the release of said connection is solely under control from said central station.

2. In a telegraph system, a first'station, a second station, a line connecting said stations, an isochronous-code sender at said first station, a numerical automatic switch at said first station, means to control said switch selectively to connect said sender to said line, a source of alternating current at said first station, a manual key at said first station adapted to connect said source through said switch to said line, and an audible-signal device at said'second station and responsive to said source.

3. In a telegraph system, a first station, a second station, a signaling line connecting said stations, an isochronous-code sender at said first station, a source of alternating current of determined frequency at said first station, a frequency-selection-responsive audible signal device at said second station and responsive to said source, a manual key adapted to connect said source to said signal device, and an automatic non-numerical switch also adapted to connect said source to said signal device. 7

4. In a telegraph system, a central station, a sub-station, a signaling line connecting said stations, a plurality of telegraph sets at said central station, automatic switching equipment at said central station and controlled by said substation to connect said signalling line to one of said telegraph sets, an audible signal at said substation, means in said automatic'switch'to operate said signal automatically in the event that said switch fails to connect said line to one of said telegraph sets, and means to operate said signal manually in the event that said switch shall have connected said line to one of said telegraph sets.

5. In a telegraph switching system, a control station, a sub-station, a line connecting said stations, an'alternating-current source at said control station, a frequency-selective signal device at said sub-station and responsive to said source, a manual key at said control station adapted to connect said source to said line, to operate said signal device, and a non-numerical automatic switch at said control station, said switch permanently associated with said line and adapted to connect said source automatically to said line to operate said signal device.

6. In a telegraph system, a central station, a remote sub-station, a signalling line connecting said stations, normally non-operating telegraph apparatus at each of said stations, switching equipment at said central station, means at said sub-station for operating said switching equipment to select said telegraph apparatus at the central station for connection to said signalling line, means responsive to said connection for starting said central and said sub-station telegraph apparatus into operation; means operative in the event that the central station apparatus is all busy for giving an audible indication thereof at said sub-station, and a manual key at said central station for operating said last means as a calling signal.

7. In a telegraph system, a first station, a second station, at said first station, an isochronous-code sender whose speed is based upon a determined frequency of permutation, at said first station, a source of alternating current of another determined frequency, at said second station, a calling signal responsive to said source only, and at said first station a numerical automatic switch, means to control said switch selectively to connect said sender to said line, and a manual key adapted to connect said source and said calling signal.

8. In a signalling system, a central station, substations, a plurality of signalling lines connecting said central station to said substations, each of said signalling lines comprising a single line conductor extending from said central station to one of said substations, telegraph apparatus at said substations including a normally non-operating motor at each substation, a telegraph set at said central station, switching means at said central station for connecting said set to a signalling line, means controlled from said central station over said connected signalling line for starting said normally non-operating motor, and means responsive to signals from said set at said central station for indicating at the central station that the substation telegraph apparatus is in operative condition.

9. In a signalling system, a first station, a secnd station, a single signalling line connecting said stations, isochronous senders and receivers at said stations, and means responsive to control signals from the sender at said first station to cause the receiver at said second station to send an isochronous signal to said first station different from said control signals to indicate that the receiver at said second station is operating in response to signals: from said first station.

10. In a signalling system, a first station,'a second station, a signalling line connecting said stations, automatic telegraph senders and receivers at said stations, and means responsive only to two complete normal cyclic selective functionings of the receiver at said second station, and effective tosend a signal to said first station.

11. In a signalling system, a first station, a second station, a signalling line connecting said stations, isochronous senders and receivers at said stations and connected to said signalling line, and signalling contact-points connected to the receiver at said second station and operable after a complete normal selective cycle of the said receiver and operating to send a complete isochronous signal over said signalling line to the receiver of said first station.

12. In a telegraph switching system, outgoing automatic switches, incoming automatic switches; two operating tables substantially alike, an outgoing service jack upon each table, an incoming service jack upon each table, a telegraph set upon each table and comprising in part a plug adapted for either jack, said sets being alike, so that either set upon either table may be used for outgoing service or for incoming service according to the jack used.

13. In a telegraph system, a substation telegraph set comprising a printer, a code-sender with normally closed electrical contacts, a motor, a calling key with normally closed electrical contacts, a polar relay, and circuits controlled by said relay to start said motor and to shunt said calling key, and, alternatively, to stop said motor and toshunt the contacts of said code-sender.

14. In a telegraph system, a substation telegraph set comprising a printer, a code-sender with normally closed electrical sending-contacts, a calling key with normally closed electrical contacts, a motor, a polar relay, a sole tongue in said relay, two contacts for said tongue, circuits whereby said sole tongue in engagement with one of said contacts operates said motor to render said sender mechanically operable, a shunt circuit closed by said tongue in engagement with said one of said contacts to shunt the contacts of said calling key, and a further shunt circuit closed by said tongue in engagement withthe other one of said contacts to shunt the contacts of said sender.

15. In a telegraph system, two service tables, two service jacks one upon each table, a'sole service line connected to both said jacks, two signal devices one for each jack and both connected to said sole service line, and contacts in each jack to render operable its associated signal device when said jack is in service, whereby a suitable electrical signal received over said line will operate the signal device solely at the jack which is then in service.

16. In a printing telegraph set, a line circuit, a transmitter and a receiving printer associated with said line circuit, a selector mechanism in said printer responsive to a controlling signal over said line circuit, and means controlled by a full cyclic operation of said selector mechanism and associated with said transmitter for transmitting a reply signal over said line circuit after the completion of said controlling signal.

1'7. In a printing telegraph system, a plurality of stations, a line circuit connecting the stations, a transmitter and a receiving printer at one of said stations associated with the line circuit, a selector mechanism for said receiving printer including a plurality of bars each responsive to a code signal over said line circuit, and means controlled upon the selection and operation of a bar of said selector mechanism of said printer for transmitting a code signal to another connected station.

18. In a printing telegraph system, a plurality of stations, a line circuit connecting the stations, a transmitter and a receiving printer at one of said stations associated with the line circuit, a selector mechanism for said receiving printer including a plurality of bars severally responsive each to a variant code signal over said line circuit, a receiving printer at a distant connected station, and means controlled through the selection and operation of a bar of said selector mechanism of said printer for transmitting a code signal effective to operate the receiving printer at the distant connected station.

19. In a signalling system, a central station and a plurality of remote stations each provided with telegraph printers, a plurality of signalling lines extending from the central station to the remote stations, a plurality of telegraph printers at said central station arranged in a predetermined sequence, automatic switching means for invariably connecting incoming calls to the lowest numbered idle printer, and means for automatically starting the motors of the printers at the central and remote stations upon the establishment of said connection.

20. In a telegraph system, a plurality of transmission lines, a central office in which said transmission lines terminate, telegraph apparatus at said central oifice common to all said lines, a motor for said telegraph apparatus, and a motorstarting mechanism for said motor responsive to conditions established upon any of said lines.

21. In a telegraph system, a central station, a plurality of sub-stations, line circuits terminating at said central station, one for each of said substations, line relays, one for each of said line circuits and controlled by said sub-stations over said line circuits, a printer and control device at said central station, and means for rendering said printer and control device responsive to conditions established by any one of said line relays.

EDWARD E. KLEINSCHMIDT. 

